5.6.1 SEMITOP® with soldered terminals
Use plastic anchor pins in each corner on the top of the SEMITOP® for mechanical connection between PCB and SEMITOP®. To avoid mechanical stress to the soldering pins, the PCB has to be additionally supported (e.g. using spacers).
Suggested hole diameter for the soldering pins and the mounting pins in the PCB is 2mm.
It does not exist a limit to the number of SEMITOP® modules that could be assembled on the same PCB;
many running applications (see figure 36) consist of many SEMITOP® modules on the same PCB and the customers never had any complaint.
Figure 36: Example of running application with multiple SEMITOP® modules on the same PCB
5.6.1.1 Soldering on PCB
SEMITOP® modules can be soldered to the PCB using the most common soldering process:
Hand iron
Wave soldering process
Selective soldering equipment
Independent on the soldering process used to solder SEMITOP® modules to the PCB, SEMIKRON recommends a thorough evaluation of the solder joints to ensure an optimal connection between SEMITOP® and the PCB.
Figure 37 shows a profile of a good soldered joint. Notice that the solder forms a concave meniscus between pin and pad. This is an example of a properly formed meniscus and it is a result of good wetting during the soldering process.
Figure 37: Good soldered joint profile
In both Figure 37 and Figure 38 it can also be seen that the soldering covers a good deal of the surface area of the pin and of the pad. This is also evidence of good wetting.
It has to be noted that the soldering joint has a smooth surface with a silver color. This is the result of good immobilization of the joint during cooling as well as good cleaning of the board prior to soldering. All soldering connections should exhibit similar characteristics regardless whether they are soldered by hand iron or wave soldering process.
Figure 38: Detail of solder joint
The time required to create a robust connection depend on several parameters:
PCB thickness: when increasing the PCB thickness, the heat dissipation capability of the PCB itself will be the higher, and thus it will require a longer soldering time
Copper wire area: pins require large copper wire to minimize resistive power losses during the current flowing. Since copper has a good heat transmission coefficient, the size of these copper wires directly affects the soldering time necessary to heat the PCB pad.
Hand iron power: power, tip size and working temperature of the hand iron affect the soldering time.
These parameters have to be adjusted in order to keep the maximum temperature within the specified limit.
Lead free solder alloys type: Sn content is the key leading component that affects the soldering time and temperature. Normally used lead free alloys are Sn96.5Ag3Cu0,5 or Sn99Cu0,7.
SEMIKRON recommends that the soldering joints should be thoroughly checked to ensure a high quality soldering joint. If necessary, different parameters should be adjusted in order to optimize the process.
A) Hand Soldering
SEMIKRON recommends to not exceed the maximum temperature of 260°C for a soldering time of 10seconds especially when several terminations must be soldered.(CEI-EN 60068-2-20).
B) Wave Soldering Profile SEMIKRON recommends:
do not exceed the maximum wave soldering profile of figure 39;
the maximum preheating temperature has to be kept under or equal to the maximum storage temperature (125°C);
do not exceed the maximum preheating time of 100seconds;
during the soldering phase, do not exceed the maximum soldering time of 10 seconds at the maximum temperature of 245°C±5°C.
Figure 39: Wave soldering profile
SEMITOP® modules could be soldered by a deep soldering process; the important is to avoid to exceed the maximum soldering conditions stated in the previous items.
5.6.2 Connecting the PCB via press-fit pins
The following requirements as regards the Plated Through Hole (PTH) of the PCB need to be fulfilled according to international standard IEC 60352-5 in order to ensure the proper functioning. SEMIKRON performed all the qualification tests following these requirements. The qualification tests were done using a standard FR4 PCB with an immersion tin (I-Sn) surface finish.
The following table shows the specification of the PTH:
Table 22: Specification of PTH for the press-in process Min. Typ. Max.
Recommended size of drill 1.6mm
Drilled hole diameter 1.575mm 1.6mm 1.625mm Copper thickness in via 25m
Tin plating in via 0.5m
Final hole diameter 1.39mm 1.45mm 1.54mm Cu width of the Annular ring 100m
Thickness of PCB 1.6mm
In case of soldering of Press-Fit pins directly to the PCB, the following table shows the PTH specification:
Table 23: Specification of PTH for soldering of Press-Fit pins to the PCB Min. Typ. Max.
Drilled hole diameter 2.10mm 2.15mm 2.25mm Copper thickness in via 25m
Tin plating in via 10m
Final hole diameter 2.00mm
Cu width of the Annular ring 100m
Thickness of PCB 0.8mm 1.6mm
The recommended hole diameter for the mounting post to fix the SEMITOP® Press-Fit to the PCB should be in accordance with the following table:
Table 24: Specification of PCB hole diameter for the mounting post Module type Diameter [mm]
SEMITOP4® Press-Fit 3.6
SEMITOP3® Press-Fit 2
SEMITOP2® Press-Fit 2
Mounting post
Particular attention must be paid for those components that need to be placed close to module pins like resistors, capacitors or diodes. A minimum distance of 4mm is required between the edge of these components and the middle of PTH; this ensures enough space for the pressing tool.
Figure 40: Distance between components and center of PTH
As the definition itself of press-fit module says, it is needed to press-in the module into the PCB for a perfect match. The available presses suitable for this process can be categorized as manual, force assisted manual, semiautomatic and fully automatic. For further details about the press-type characteristics, please refer to the SEMITOP® Press-Fit mounting instructions.
SEMIKRON qualified the press-fit technology and process by using an electric press by KISTLER.
5.6.2.1 Press-in process
The press-fit technology works well when the right electrical contact between pin and PCB is ensured. The press-fit pins therefore have to be pressed in correct depth into the holes of the PCB. To ensure a proper press-fit contact, the center of the press-fit pin head has to be at least 0.5mm below the top surface and at least 0.5mm above the bottom surface of the PCB (refer to the following picture).
Figure 41: Press-in depth in PCB
The following parameters are based on SEMIKRON press-in tool in use:
Press-in force per terminal: 95±10N
Press-in speed: 5-10mm/s
In case the press-machine is equipped with the possibility to record the force-stoke values during the press-in process, some relevant values should be considered. Details about the typical vs stroke profile
Center of press-fit pin head
min. 1.6mm
min. 0.5mm min. 0.5mm
5.6.2.2 Press-out process
The press-out tool allows to disassemble the module from the PCB. The following parameters are based on SEMIKRON press-in tool in use:
Press-out force per terminal: > 40N
Press-out speed: 2-5mm/s
In case the press-machine is equipped with the possibility to record the force-stoke values during the press-out process, some relevant values should be considered. Details about the typical vs stroke profile are in the SEMITOP Press-Fit Mounting Instructions.
5.6.2.3 Reworking of the assembly “module and PCB”
Each SEMITOP® Press-Fit type can be used only once. In case the system “module+PCB” needs to be disassembled, following options are possible:
Module can be reused by soldering the press-fit pins to the PCB. Due to the pin deformation by the initial press-in process, any additional press-in process will result in low holding forces between the terminal and the PCB hole and is therefore not recommended.
PCB can be reused. The number of times depends on the plating of the via :
Sn > 0.5µm: PCB can be disassembled and used two additional times
Au 0.05 - 0.2m over 2.5 - 5m Ni: PCB cannot be reused.
5.6.3 PCB starter kit
5.6.3.1 Demo PCB board for GD topology, SEMITOP®4 soldered terminals Figure 42: Demo PCB for GD topology: outer dimension and schematic
5.6.3.2 Demo PCB board for DGDL topology, SEMITOP®4 soldered terminals Figure 43: Demo PCB for DGDL topology: outer dimension and schematic
These PCBs are intended only for testing purpose and not for mass production.
These demo boards are intended for dynamic test and therefore they are a low stray inductance design.
The boards allow as well the use of capacitors and resistor for DC link precharge circuit.
Recommendation: 4 electrolytic capacitors 330uF 400V 4 resistors 68kW/4W, 1 resistor 330W/4W
Suggested hole diameter for the solder pins in the circuit board is 2mm. Suggested hole diameter for the mounting pins in the circuit board is 3,6mm.
Both demo PCB boards are available on request.
Components such as connectors, SMDs etc., are not included in the shipment.